The objectives of this research proposal are: (1) Extension of our knowledge about the structural and conformational requirements of thyroxine-binding globulin (TBG) for the binding of thyroid hormones. Techniques such as selective use of denaturants to explore structure and conformation through the determination of denaturation kinetics, fluorescent analysis using covalently and bonded chromophores as reporter groups, and solvent perturbation and hydrogen exchange to study localized conformational changes accompanying ligand binding. (2) Investigation of the binding of desialylated TBG to rat liver plasma membranes and application of an inhibition assay using the plasma membrane system for detection of circulating desialylated glycoproteins in normal human serum and in serum from patients with hepato-biliary disease. (3) Quantitation of levels of circulating desialylated glycoproteins in serum from patients with hepatic disease and correlation of these levels with the clinical state of the disease to provide a prognostic tool for following hepatocellular damage. (4) Measurement of levels of desialylated glycoproteins in cerebrospinal fluid and correlation of these levels with central nervous system disease. (5) Determination of the intracellular location within hepatocytes of desialylated DTBG by means of immunocytochemical and electron microscopic studies after preparation of an Fab antibody fragment of antihuman TBG antibody. (b) Investigation of the microheterogeneity of purified TBG by isoelectric focusing of the protein in a free medium on a preparative scale so that adequate amounts of each of the resolved components can be recovered for study of their thyroxine binding and antigenicity. BIBLIOGRAPHIC REFERENCES: Studies on Human Thyroxine-Binding Globulin (TBG): IX. Some Physical, Chemical, and Biologic Properties of Radioiodinated TBG and Partially Desialylated TBG (STBG). Refetoff, S., Fang, V.S. and J. S. Marshall. J. Clin. Invest. 56:177, 1975.